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Abstract
An RP‐HPLC method with photodiode array detection and electrospray ionization mass spectrometry was established for the determination of major caffeic acid derivatives (caftaric acid, chlorogenic acid, cynarin, and cichoric acid) in commercial Echinacea purpurea dietary supplements. The samples were extracted with 60% methanol (3 × 15 mL) by means of sonication at room temperature. The components of interest were separated on a RP‐18 chromatography column using a 20‐min water–methanol–trifluoroacetic acid (TFA) gradient, identified by photodiode array detection, and further confirmed by LC‐ESI‐MS. The quantification was performed using external standards. The sample preparations and stability of the methanolic extracts were extensively explored. Analyses of 16 commercial E. purpurea products revealed that there is a considerable variability in the content of the caffeic acid derivatives among the products tested. The current method may serve as a valuable tool for the Quality assurance (QA)/Quality control (QC) of echinacea dietary supplements.
Acknowledgments
This research was supported by the Functional Food for Health Program, University of Illinois, the Office of the Vice Chancellor for Research, University of Illinois at Chicago and by Grant Number P50 AT00155 provided by the National Center for Complementary and Alternative Medicine (NCCAM), the Office of Dietary Supplements (ODS), the Office for Research on Women's Health (ORWH), and the National Institute of General Medicine (NIGMS) of the National Institutes of Health (NIH). The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of the NCCAM, ODS, ORWH, NIGMS or NIH.